Hazelnuts are popular, valued for their rich flavor and dense nutritional profile, including healthy fats, fiber, and protein. As consumers become more aware of plant compounds, many are asking about the presence of oxalates in their favorite foods. Oxalates are naturally occurring substances found in many plants, and their presence in dietary staples like nuts has become a concern for some individuals. Understanding the concentration of these compounds in foods like hazelnuts is key to assessing their role in a balanced diet.
What Are Oxalates and Their Dietary Relevance
Oxalates, or oxalic acid, are small organic molecules produced by plants as a byproduct of metabolism. They have a strong ability to bind to positively charged minerals. In plants, oxalates often accumulate as calcium oxalate crystals, helping regulate calcium levels and acting as a defense mechanism.
Oxalates are considered anti-nutrients because they bind with minerals like calcium and magnesium in the digestive tract, reducing their bioavailability. The primary dietary concern relates to the formation of calcium oxalate kidney stones, which account for the majority of all kidney stones.
Foods contain both soluble and insoluble oxalates. Soluble oxalates are the form most readily absorbed by the body in the small intestine, raising the concentration of oxalate in the urine. Once absorbed, soluble oxalate can combine with calcium to form insoluble calcium oxalate crystals, which may lead to stone formation.
Hazelnuts and Their Oxalate Content
Hazelnuts contain a measurable amount of oxalates, placing them in the moderate-to-high range among nuts. Studies report total oxalate content in raw hazelnuts ranging from approximately 140 to over 220 milligrams (mg) per 100 grams. This level is higher than that found in walnuts, which typically contain less than 70 mg per 100 grams.
Hazelnuts contain significantly less oxalate than high-oxalate nuts like almonds, which can contain between 370 and 470 mg per 100 grams. For context, extremely high-oxalate vegetables like spinach can contain over 1,000 mg per 100 grams. Therefore, hazelnuts fall closer to the middle of the spectrum when considering all plant-based foods.
The key factor for dietary risk is the soluble oxalate content, as this is the fraction absorbed in the gut. This bioavailable fraction contributes to the moderate-to-high categorization of hazelnuts. Total oxalate content can also fluctuate based on factors like the growing region, cultivar, and specific processing methods used.
Preparation can influence the final oxalate level, though the effect is less dramatic than with vegetables. Roasting nuts does not typically cause a significant reduction. However, processing involving water, such as soaking or blanching, may allow some soluble oxalate to leach out.
Strategies for Managing Oxalates in Your Diet
Individuals prone to kidney stones or advised to follow a low-oxalate diet can manage intake from foods like hazelnuts using several strategies.
Pairing with Calcium
One of the most effective methods involves pairing oxalate-containing foods with a source of calcium. When calcium is consumed alongside oxalates, the two compounds bind together in the digestive tract. This forms an insoluble complex that is harmlessly excreted in the stool.
This binding prevents soluble oxalate from being absorbed into the bloodstream and concentrated in the kidneys. For example, consuming hazelnuts alongside a dairy product or other calcium-rich food can mitigate the nut’s oxalate content.
Other Management Techniques
Other techniques focus on reducing intake and promoting excretion:
- Portion control is a fundamental strategy, as the total amount of oxalate consumed is directly proportional to the serving size.
- Food preparation methods, such as boiling or soaking and then discarding the water, can remove some soluble oxalates from foods like vegetables and legumes.
- Maintaining a high fluid intake is important because increased water consumption helps dilute the concentration of oxalate in the urine, making crystal formation less likely.
- Focus on dietary variety to avoid over-relying on high-oxalate foods, rotating between lower-oxalate nuts (like macadamias or pecans) and moderate-oxalate nuts (like hazelnuts).
Consulting with a healthcare professional or a registered dietitian can provide personalized guidance tailored to specific health needs.